A directed continuum damage mechanics method for modelling composite matrix cracks

Matrix cracking in continuous fibre reinforced composites follows the fibre orientations, but continuum damage mechanics models are not able to properly capture this. A novel method is presented here to alleviate mesh sensitivity of the damage growth direction and represent discrete matrix cracks. In a ply-by-ply mesoscale model, matrix cracks within a ply usually rely on mesh dependent strain localisation to decide the crack growth direction. The newly proposed algorithm instead uses the ply level fibre orientation as a model input, and maintains crack advancement along this direction, based on a neighbour searching scheme. A further advantage is that it is able to represent individual cracks discretely, with a predefined minimum crack spacing. This overcomes another limitation of continuum damage models, where discrete cracks are only represented in a smeared sense. This procedure has been shown to be able to reproduce complex crack networks in multidirectional laminates, independent of the mesh pattern.